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Tail Stars

StarDate:

October 23, 2013

Many constellations have a star that represents the character’s tail. Their names begin with the Arabic word for tail, Deneb. The most famous are the tail of the swan, known simply as Deneb, and the tail of the lion, Denebola. Two lesser-known tail stars are in view in the southern sky this evening: Deneb Algedi, in Capricornus, the sea-goat, and Deneb Kaitos, in Cetus, the whale.

Deneb Algedi is a good bit bigger and hotter than the Sun, and much farther along in life. In fact, it’s probably around the end of its “normal” lifetime, when it burns the hydrogen in its core to make helium. If so, then it’s getting ready to puff up to giant proportions as it prepares to burn the helium to make carbon.

Deneb Kaitos is already burning its helium, so it’s even bigger and brighter than Deneb Algedi. That extra brightness makes the star clearly visible across almost a hundred light-years of space.

It’ll continue consuming the helium for another hundred million years or so. When it’s done, it’ll cast its outer layers into space, forming a bright bubble known as a planetary nebula. When the nebula dissipates, only the star’s hot, dead core will remain, shining meekly as it slowly cools over the eons.

Capricornus is in the south at nightfall, to the upper right of Fomalhaut, the only bright star in that region of the sky. Its tail is at the left end of a wide triangle. The tail of Cetus is about the same distance to the left of Fomalhaut.

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